Theoretical search for half-Heusler topological insulators

TL;DR

This study uses ab-initio calculations to identify new half-Heusler compounds, LiAuS and NaAuS, as topological insulators with significant bulk gaps and unique surface states, advancing the understanding of topological materials.

Contribution

The paper introduces two new half-Heusler topological insulators with finite bulk gaps and distinctive surface state properties, expanding the class of topological materials.

Findings

LiAuS and NaAuS are strong topological insulators with 0.20 and 0.19 eV gaps.

Surface states exhibit p-type and n-type carriers due to structural inversion asymmetry.

Topological properties are robust against in-plane strains.

Abstract

We have performed ab-initio band structure calculations on more than two thousand half-Heusler compounds in order to search for new candidates for topological insulators. Herein, LiAuS and NaAuS are found to be the strongest topological insulators with the bulk band gap of 0.20 and 0.19 eV, respectively, different from the zero band gap feature reported in other Heusler topological insulators. Due to the inversion asymmetry of the Heusler structure, their topological surface states on the top and bottom surfaces exhibit p-type and n-type carriers, respectively. Thus, these materials may serve as an ideal platform for the realization of topological magneto-electric effects as polar topological insulators. Moreover, these topological surface states exhibit the right-hand spin-texture in the upper Dirac cone, which distinguish them from currently known topological insulator materials. Their topological nontrivial character remains robust against in-plane strains, which makes them suitable for epitaxial growth of films.